1. Field of the Invention
The present invention relates to an internal combustion engine provided with an electromechanical transducer having the functions of an electric motor and an electric generator, an electric motor or a generator.
2. Description of the Related Art
An engine provided with an electromechanical transducer disposed in a crankcase and capable of operating as both a motor and a generator is disclosed in JP-A 182371/1997. The electromechanical transducer of this prior art engine has a permanent magnet attached to the large end of a connecting rod connecting a reciprocating piston and a crankshaft, and a stator coil placed on a base fixed to a crankcase formed of a lower part of a cylinder block and an oil pan attached to the cylinder block. The permanent magnet revolves together with the large end of the connecting rod relative to the stator coil as the crankshaft rotates. Consequently, an electromotive force is generated in the stator coil by the electromagnetic interaction between the permanent magnet and the stator coil, and the electromechanical transducer functions as a generator. When an ac current is supplied to the stator coil from a battery, an electromagnetic force is exerted on the permanent magnet in a direction tangent to the path of revolution of the permanent magnet by the electromagnetic interaction between the ac current and the permanent magnet, and the electromechanical transducer functions as a motor.
In this prior art engine, the large end of the connecting rod holding the permanent magnet revolves about the axis of the crankshaft and turns alternately in opposite directions about the axis of a crankpin connected to the large end of the connecting rod. Therefore, the size of a gap between the permanent magnet and the stator coil cannot be maintained if constant, the gap is narrowed to the least size only for a very short time, and hence the electromechanical transducer is unable to function efficiently as a motor or a generator.
The present invention has been made in view of such a problem and it is therefore a first object of the present invention to provide an internal combustion engine provided with an electric device having a magnetic member and a coil, such as an electric motor, a generator or an electromechanical transducer, formed in a comparatively small size, and capable of constantly maintaining a small gap between the magnetic member and the coil while the magnetic member is opposite to the coil.
A second object of the present invention is to improve, when the electric device is an electric motor, the effect of the electric motor in assisting the rotation of a crankshaft included in the internal combustion engine, to improve, when the electric device is a generator, the power generating efficiency of the generator, and to suppress increase in the weight of the internal combustion engine.
According to the present invention, an internal combustion engine comprises: a cylinder block, a crankshaft, a bearing cap fastened to the cylinder block so as to hold the crankshaft for rotation on the cylinder block, and a crank chamber forming member forming a crank chamber; wherein magnetic field creating members are fixed to parts of the crankshaft in the crank chamber so as not to move relative to the crankshaft, coils are held on the bearing cap in the crank chamber, and the magnetic field creating members and the coils form at least electric motors, generators or electromechanical transducers.
According to the present invention, since the magnetic field creating members and the coils forming electric motors, generators or electromechanical transducers are held on the crankshaft and the bearing cap disposed in the crank chamber, the effect of combination of the electric motors, the generators or the electromechanical transducers with the internal combustion engine on increase in the size of the internal combustion engine is suppressed. Since the magnetic field creating members are fixed to the crankshaft, the small gap between the magnetic field creating members and the coils held on the bearing cap can be easily maintained constant while the magnetic field creating members turning together with the crankshaft is opposite to the coils. Thus, a large assistant force assisting the rotation of the crankshaft can be generated when the magnetic field creating members and the coils form electric motors, and power can be generated at a high power generating efficiency when the magnetic field creating members and the coils form generators. Since the coils are held on the bearing cap, the coils can be attached to and removed from the cylinder block together with the bearing cap, which facilitates work for installing the coils in the crank chamber, the coils can be effectively cooled by a large amount of oil lubricating the main bearings of the internal combustion engine, and, consequently, the electric motors, the generators or the electromechanical transducers operate at a high efficiency.
The bearing cap may comprise a plurality of bearing cap bodies and connecting member connecting the bearing cap bodies, and the coils may be disposed on the side of the axis of the crankshaft with respect to the connecting members.
Thus, the coils can be firmly fastened to the bearing cap, which is advantageous to maintaining the gap between the magnetic field creating members and the coils constant. Since the coils are disposed in a space on the side of the axis of the crankshaft with respect to the connecting member, the coils do not increase the size of the internal combustion engine.
The bearing cap may include a plurality of bearing cap bodies and a connecting member connecting the bearing cap bodies, and the coils may be held on the connecting member.
Thus, the magnetic field creating members and the coils can be disposed at long distances, respectively, from the axis of the crankshaft. Therefore, a high assistant torque assisting the rotation of the crankshaft can be produced when the magnetic field creating members and the coils form electric motors. Since the magnetic field creating members move at a high circumferential speed, power can be generated at a high generating efficiency when the magnetic field creating members and the coils form generators. Since the coil is held on the connecting member for enhancing the rigidity of the plurality of bearing cap bodies, the coils can be firmly held on the highly rigid connecting member, which is advantageous to maintaining the small gap between the magnetic field creating members and the coils constant.
According to the present invention, an internal combustion engine includes: a crankshaft, and crank chamber forming members forming a crank chamber; wherein magnetic field creating members are fixed to parts of the crankshaft in the crank chamber, coils are held on the crank chamber forming members in the crank chamber, and the magnetic field creating members and the coils form at least electric motors, generators or electromechanical transducers.
The construction according to the present invention suppresses the effect of the formation of electric motors, generators or electromechanical transducers in the internal combustion engine on increasing the size of the internal combustion engine. Since the magnetic field creating members are fixed to the crankshaft, the small gap between the magnetic field creating members and the coils held on the crank chamber forming members can be easily maintained constant while the magnetic field creating members turning together with the crankshaft is opposite to the coils. Thus, a large assistant force assisting the rotation of the crankshaft can be generated when the magnetic field creating members and the coils form electric motors, and power can be generated at a high power generating efficiency when the magnetic field creating members and the coils form generators.
The coils may be held on coil holders disposed in the crank chamber so that the gap between the magnetic field creating members and the coil can be maintained constant.
Thus, the small gap between the magnetic field creating members and the coils held on the coil holding chamber can be easily maintained constant while the magnetic field creating members turning together with the crankshaft are opposite to the coils, a large assistant force assisting the rotation of the crankshaft can be generated when the magnetic field creating members and the coils form electric motors, and power can be generated at a high power generating efficiency when the magnetic field creating members and the coils form generators.
Desirably, the magnetic field creating members are held on balance weights included in the crankshaft. Thus, the magnetic field creating members serve as balance weights, increase in the weight of the internal combustion engine by the combination of electric motors, generators or electromechanical transducers with the internal combustion engine can be suppressed, and increase in the size of the internal combustion engine can be suppressed because the balance weights are originally disposed in the crank chamber.
The crank chamber forming members may include an oil pan, and the coils may be immersed in oil contained in the oil pan. Thus, the coils can be effectively cooled by a large amount of oil contained in the oil pan and, consequently, the electric motors, the generators or the electromechanical transducers operate at a high efficiency.